Line Of Duty has teased fans with the possibility that the season finale will at last revel the identity of the elusive H.
The trailer for the seventh and final episode of the sixth series of the BBC police drama has been released with Superintendent Ted Hastings declaring, "All of these suspicious deaths were orchestrated by one officer in particular - H, The Fourth Man."
Since Line Of Duty — written by Jed Mercurio and starring Vicky McClure, Martin Compston and Adrian Dunbar — first began in 2012 the police anti-corruption unit AC-12 has been investigating the identity of a corrupt senior police officer who is working with an Organised Crime Group, and currently known as 'H'.
The trailer teases: "Every investigation... has led... to this", before the words disappear from the screen leaving only the letter 'H'.
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The current series also stars Kelly McDonald as suspected corrupt officer DCI Jo Davidson, Saffron Davies as new AC-12 member Chloe and Anna Maxwell Martin as the ominous DCS Patricia Carmichael who has taken over command of AC-12.
The trailer also shows a police memo with the word definitely spelt incorrectly as "definately" highlighted. Earlier in the series the unidentified criminal giving DCI Davidson her orders over a computer misspelt "definately" the same way.
The trailer ends with the team chasing and cornering an armed suspect wearing a balaclava.
The BBC has revealed the penultimate episode of the current series of Line of Duty has broken the show's ratings record, becoming its most-watched episode ever.
It secured an average of 11 million viewers and 51.7% of the audience share, the broadcaster shared on Twitter.
Creator Jed Mercurio said: Thanks so much to everyone watching #LineofDuty6. The whole production team is thrilled and flattered by the amazing response."
Line of Duty concludes on Sunday 2 May at 9pm on BBC One and BBC iPlayer.
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